Translation:It is a small bed, isn't it?
"Is not it a small bed?" rolls so so well off the tongue compared to "Isn't it a small bed?" Lol
Kidding. Clearly my joke example is more colloquial and not 100% grammatically correct, and thus less formal, but the whole sentence in Japanese expresses a casualness that would be roughly equivalent to us changing the grammar in English.
Point being: we should have the option to translate more liberally at times.
From a dictionary (大辞泉), 小さい (i-ending) has a more objective perspective, and 小さな (na-ending) has a relatively subjective meaning. e.g. 小さいベッド is small in measurement, which,小さなベッド maybe not small in mersurement, but it gives a feeling of small (e.g. has a lot of things on it or the style of the bed making it looks small)
The ね at the end of ですね is added to, hmm, sort of invite either agreement on a sentiment or confirmation of information (depending on context) from the person being addressed. In this case, it's the former, hence the "isn't it" part of the English translation.
"What a small bed" implies more of an exclaimation or even a criticism, which is not quite the tone they're going for here.
As an adjective - good question, and hard to answer. In many cases I'd say they're interchangeable, including here, though my mental picture of a "little bed" and a "small bed" would have the former be something much smaller (in fact, if you were commenting on beds in a dollhouse, say, you'd be far more likely to use 'little' than 'small'). In other cases, e.g. "a little coffee" vs "a small coffee", they're not interchangeable - the former implies some indetermine low quantity of it, whereas the latter implies a known fixed-size serving. It's relatively unusual to say "a small bit of", and likewise "a little portion" or "a little size" (vs. "does that come in a small size"?)
In colloquial English (California) Huh is used like right. Therefore, would you say that, "It is a small bed, huh?" is correct? I feel that the "ne" particle ending is colloquial Japanese seeking agreement. The fact that the correction sometimes only lists it as a simple interrogative is incorrect. "It is a small bed?" Is wrong.
Because it is not a question at all in the Japanese sentence. In other words, "isn't it?" is not a perfect translation to the ね particle. It conveys the meaning of "I hope you agree" but nothing in English can translate to this particle perfectly.
Even if it is a question in the Japanese sentence, most likely you will see a か particle at the end, but still no question marks, because traditionally Japanese language does not have this symbol "?". Ending particle か makes a sentence a question.
Couldn't this be translated as "What a small bed!"? Like the Japanese sentence, it prompts others to comment on the object of the interjection, but is phrased kind of like a question if taken literally. As I understand it, "ne" can not only be used when you want someone to comment on what you said, but also as a sort of exclamation point to punctuate your emotion (such as surprise.)